Trees and Constituents

Midterm Exam Nov. 21pm to 4pm

• Room: 3002 NSH• Open book

– But no internet or cell phone• May bring food.• May step outside to smoke.• May go to restrooms. • May ask questions.

Summary: Parts of Speech

• Claim:– Parts of speech can be defined by

• Distribution – where they appear• Morphology – which prefixes, suffixes, etc apply to them

• Each criterion of distribution or morphology is called a test.

• Methodology– Identify relevant tests– Apply tests– Judge grammaticality– Interpret results

Annotation

• The Test methodology is state of the art for annotation projects, including many treebanking projects.

Trees and Constituents

Grammars and Lexicons11-721

September 10, 2007

Phrasal Categories

This boy must seem incredibly stupid to that girl.Det Noun Modal Verb Adverb Adjective Prep. Det Noun

Noun Phrase Adjective Phrase

Prepositional Phrase

Noun Phrase

Verb Phrase

Sentence

Phrasal Categories

• NP: Noun Phrase

• VP: Verb Phrase

• PP: Prepositional Phrase

• AP: Adjective Phrase

• AdvP: Adverb Phrase

• S: Sentence

Tree Terminology• Mother• Daughter• Sister• Dominate• Immediately Dominate• Node (branching or non-branching)• Branch • Terminal Node/Leaf Node• Phrasal Nodes (non-terminal)• Lexical Nodes (pre-terminal)

Constituent

• A constituent is a string of words such that there is one node that dominates those words and no other words.

Sam climbed up the ladder.

Sam picked up the ladder.

N V P Det N

N V P Det N

NPNP

NP

VP

S

V

NP

VPPP

S

Tree 1

Tree 2

Discussion

• What are the constituents of Tree 1 and Tree 2?

• Which strings of words are constituents in one tree but not the other?

Coordination as a diagnostic test for constituency

• To test whether a string of words s1 is a constituent, conjoin it using and with another string which– Is an uncontroversial constituent of the same

category as s1 or– (If you don’t have a hypothesis about the

category of s1), has the same part of speech sequence as s1

Applying the coordination test

• Sam climbed [up the ladder] and [out the window].

• *Sam picked [up a ladder] and [out some new boots].

Movement as a test for constituency

• A constituent might appear in different positions in a sentence, but stay in one piece.

• There are different movement rules that affect different constituents (NP, PP, AP, VP).

Begin side track for some extra background

Transformational Grammar and Movement Rules

S

NP VP

The kids V NP

ate the chocolate

Deep Structure

S

NP VP

The chocolate V PP

was eaten by the kids

Surface Structure

Meaning preserving tree-to-tree mapping

Transformational Grammar1. Sentences that mean the same thing have the same deep

structure.2. Tree-to-tree mappings convert deep structure trees into

surface structure trees.3. Tree-to-tree mappings must be meaning preserving, so

that (1) remains true.4. Government and Binding Theory and the Minimalist

Program (Chomsky) are theories that characterize which tree-to-tree mappings are meaning preserving.

1. The kids ate the chocolate.2. The chocolate was eaten by the kids. (meaning preserving)3. The chocolate ate the kids. (not meaning preserving)

Non-Transformational Grammar• In this class, we will not use transformational

grammar.• There will be no tree-to-tree mappings.

(There will be other kinds of mappings.)• The canonical representation of meaning will

not be a deep structure tree.• There will be a different way to connect

sentences that mean the same thing.

Movement is still a useful metaphor at this stage in the course

• Sam climbed up a ladder.• Up a ladder Sam climbed up a ladder.• Sam likes chocolate.• It is chocolate that Sam likes chocolate.

End side track

To use movement as a test for constituency

• First, identify a meaning preserving movement rule (tree-to-tree mapping).

• Give an example showing this movement rule applying to an uncontroversial example:– Sam ran into the room.– Into the room Sam ran.

Applying the movement test

• Then apply the same rule to a controversial example that you want to test.

• Sam climbed up a ladder.• Up a ladder Sam climbed. passes the test• Sam Picked up a ladder.• *Up a ladder Sam picked. fails the test

Another movement rule

• Identify a meaning preserving movement rule and illustrate it with a non-controversial example:– He ran into the room.– It was into the room that he ran.

• Apply the movement rule to the controversial examples that you want to test.– He climbed up a ladder.– It was up a ladder that he climbed. passes the test– He picked up a ladder.– *It was up a ladder that he picked. fails the test

Be sure that you are testing the right thing

• Are these sentences relevant in showing Tree 1 and Tree 2 have different structures?– It was a ladder that Sam climbed up.– It was a ladder that Sam picked up.– Sam climbed up a ladder and a wall.– Sam picked up a ladder and a rope.– ?*A ladder was climbed up by Sam.– A ladder was picked up by Sam.– A ladder he climbed up.– A ladder he picked up.

Discussion

• Test each sentence with coordination and movement tests for Tree 1 and Tree 2.– I took out the garbage.– I turned off the light.– I turned off the highway.– I fell off my bike.– I looked up the number.

Constituency of Verb Phrases

A class participation exercise(based on Radford, Chapter 3, exercise IX)

• Goals of the exercise: – Relying on tests when your intuition fails– Adapting to inconsistent results

• (e.g., find evidence for disqualifying some of the tests)• The five trees on the following slide have all been proposed by

linguists, in published articles, for the sentence: He has been writing a letter.

• Unlike the previous exercise with particles and PPs, people do not have good intuitions about which structure is correct.

• We will learn several more tests for constituency, and apply them to these sentences in order to pick one of the trees as the correct one.

• The answer comes out different every year (depending on grammaticality judgments and creativity in finding evidence for disqualifying some tests).

TREE 1

He has been writing a letter.NP PERF PROG V NP

AUX VP

S TREE 2

He has been writing a letter.NP V NP

V VPV VP

SVP TREE 3

He has been writing a letter.NP V NP

V VP

VP

S

AUX

TREE 4NP PERF PROG V NP

AUX

V

VP

S

He has been writing a letter.

He has been writing a letter.NP V V NP

AUX VP

SVP

TREE 5

Test 3: Deletion

• A constituent can be deleted, if you can identify an appropriate meaning-preserving deletion rule.

Verb Phrase Deletion• A meaning preserving deletion rule for VP

(verb phrases): – John was writing a letter and Bill was writing a letter too.– John was writing a letter and Bill was writing a letter too.– John was writing a letter and Bill was too.

• Condition: you need to leave behind an auxiliary verb or insert do if there was no auxiliary verb.– John wrote a letter and Bill wrote a letter too.– John wrote a letter and Bill did too.

Note to myself. Feel free to read it.

• John wrote a letter and Bill too.• Stripping, not verb phrase deletion.• Sam likes chocolate, and vanilla too.• Sam likes chocolate and Sam likes vanilla too.• Looks like a non-constituent was deleted (so it’s

not left-peripheral ellipsis either). • It is still a test for constituency because the piece

left behind has to be a constituent (I think).

Test 4: Pro-Forms

• A pronoun can substitute for a noun:– Sam went to school.– He went to school.

• Other pro-forms can substitute for other parts of speech.

A Pro-VP: Do so• Put do in the same form as the verb you are

substituting it for.– The English verb forms are base, present, past, present

participle, and past participle.• John wrote a letter and Bill wrote a letter too.• John wrote a letter and Bill did so too.

– Write and do are in the past tense.• John was singing and Bill was singing too.• John was singing and Bill was doing so too.

– Sing and doing are present participles.

A meaning-preserving movement rule for VPs

– I thought he was singing and he was singing. – I thought he was singing and singing he was singing.– I thought he was singing and singing he was.

• Like Verb Phrase Deletion, this movement rule must leave an auxiliary verb behind. If there is no auxiliary verb, insert do as an auxiliary verb. – I thought he would sing a song and he did sing a song. – I thought he would sing a song and sing a song he did.

Test 5: Adverb Placement

• Sentence Adverb:• Probably he can rely on my

support.• He probably can rely on my

support.• He can probably rely on my

support.• ?He can rely probably on

my support.• ?He can rely on my support

probably.

• VP Adverb:• *Completely he can rely on

my support.• *He completely can rely on

my support.• He can completely rely on

my support.• He can rely completely on

my support.• He can rely on my support

completely.

Adverb placement

• Sentence adverbs must be immediately dominated by a node labeled S.

• VP adverbs must be immediately dominated by a node labeled VP.

Non-Constituent Coordination

• John found the letter and Bill signed the letter.


John found the letter

NP V Det N NP VP

S

Non-Constituent Coordination

• I gave a book to Mary and gave a letter to Sue.


I gave a book to Mary

NP V NP PP

VPS

Right Node Raising

• If you conjoin two strings of words that have identical final constituents, delete the first instance of the identical constituent.


Left Peripheral Ellipsis

• If you conjoin two strings of words that have identical initial constituents, delete the second instance of the identical constituent.


Trees and Constituents

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